Volume indicator for anesthesia machine system



June 21', 1966 J. o. ELAM 3,256,876

VOLUME INDICATOR FOR ANESTHESIA MACHINE SYSTEM Original Filed Aug. 21,1958 27 26 r- Z'J 2/ ATTORNEY the bellows at each inhalation.

3,256,876 VGLUME INDICATOR FGR ANESTHESIA MACHINE SYSTEM James 0. Elam,Elma, N.Y., assignor t Air-Shields, Inc., Hatboro, Pa., a corporation ofDelaware Qantinuation of application Ser. No. 756,418, Aug. 21,

1958. This application Mar. 6, 1962, Ser. No. 177,926

' 3 Claims. (Cl. 12829) The present application is a continuation of theapplication filed by me on August 21, 1958, Serial No. 756,418, nowabandoned.

This invention relates to equipment for use with anesthesia machines andis more particularly concerned with improvements in devices forindicating the volume of ventilation being provided.

In the administration of anesthesia the patient at times may be assistedin the breathing process by the anesthetist. For this purpose theanesthesia machine usually incorporates a flexible bag member to whichmanual pressure is applied to assist in the inhalation phase of thebreathing cycle, the flexible bag being connected to the anesthesia gassystem. When pressure is relieved on the system by removing the manualpressure to the bag the exhalation phase of the cycle occurs. When thepatient is breathing spontaneously the bag expands and retracts inresponse to the exhalation and inhalation phases. It is an object of thepresent invention to provide improved equipment to indicate theventilation being supplied while retaining the customary breathing baghaving the feel to which the operator is accustomed. Another objectiveis to accomplish the foregoing without commingling air from thebreathing bag with the anesthesia gas being supplied to the patient.

The volume of breathing gas being supplied to the patient is anindication whether adequate ventilation is being accomplished. Beingable to abserve the ventilation action at all times provides animportant check on the functioning of the apparatus and the breathing ofthe patient. An important object of the invention is the provision of abellows or similar expansible unit having an easily read scale to showthe amount of movement of This volume indicator is preferably located ina prominent position where it is readily visible to the anesthetist asto the surgeon and other personnel to permit checking.

A further object of the invention is the provision of a special reliefvalve construction actuated by the indicator device to automaticallybleed off excess ga from the anesthesia system when the indicator unitbecomes overdistended. This valve is also constructed to permit inlet ofair should the supply of anesthesia gas be insuflicient thus permittingthe indicator unit to become collapsed.

Another object of the invention is the provision of an arrangement ofindicator bellows and valve which prevents the accumulation of condensedmoisture which might aflect the operating characteristics.

How. the foregoing and other objects and advantages of the invention areaccomplished will be clear by reference to the drawing in which:

FIGURE 1 shows a volume indicator device according to the presentinvention and its relationship to the anesthesia machine system.

United States Patent 0 M 3,255,876 Patented June 21, 1966 FIGURE 2 showsthe special Valve device of the indicator unit in greater detail to alarger scale.

Referring to the figures it will be seen that an anesthesia mask 5 isillustrated in FIGURE 1 having an inhalation gas connection 6 leadingfrom the supply to the mask and tube 7 which carries the exhalation gasback to the system. Suitable valves permit flow only in the direction ofthe arrows in tubes 6 and 7. The exhalation gases pass through thecarbon dioxide absorber unit 8 before being returned to the system. Thesystem pipe 9 has a connector 10 through which the lung ventilating gasi supplied. The ventilating gas contains the oxygen supply and theanesthesia 'gas supplied from tanks 10a and 10b.

Connected to the anesthesia system is the indicator thesia system pipe 9by means of pipe 16 and connector 17. A pressure indicator 18 isattached to the pipe 16 to show the pressure being developed in theanesthesia machine system.

To assist in the inhalation phase the flexible squeeze bag 19 isconnected by a channel 20 to the interior of chamber 12. Thus, manualpressure applied to bag 19 develops an internal pressure which istransferred to the interior of the chamber 12 where it is againtransferred through the medium of the bellows unit 13 to the anesthesiagas circuit. There is no communication, however, between the air in thechamber and the anesthesia gases in the bellows and conduit system.

A valve unit 21 is located at the lower end of pipe 15. Theconstructional details are shown in FIGURE 2. A valve closure member 22rests on a lower fixed plate 23 to normally close an opening 24 in plate23. Stop rods 25 are provided to limit the amount of opening of thevalve 22. A flexible tension member 26, such as a string or light chain,is attached to the valve 22 by means of a lug 27 and extends upwardlywhere it is connected to another lug 27a on the inside of the uppersurface 28 of the bellows unit 13. The length of the tension member 26is selected so as to be tight when the upper surface 28 reaches itsalmost fully extended position, just before contacting the stop 29a onthe upper surface 29'of the chamber 12.

FIGURE 1 illustrates the apparatus in full line position ready for aninhalation phase. To assist the patient in the inhalation phase theanesthetist squeezes the bag 19 which displaces the gas therein andcauses a pressure to develop in chamber 12. This application of pressureto the bellows 13 causes it to transmit the pressure to the anesthesiasystem pipe 9 thereby forcing anesthesia gas under slight pressurethrough the inhalation tube 6 to the mask unit 5 where it is deliveredto the patients lungs. Because a standard breathing bag 19 is used asthe squeeze bag, the feel of the system is generally similar to a normalsystem. Thus the operator can maintain the proper pressure and deliverthe desired volume of gas to the patients lungs. The volume beingdelivered is directly indicated by the extent that the bellows 13collapses and is read by the position of the upper surface 28a withadditional ventilating gas is provided to the system through theconnector 10 and this together with the gas returned to the system fromthe absorber unit 8 causes the bellows device 13 to again expand to itsoriginal position. This expansion of bellows 13 displaces the gas inchamber 12 into the bag 19 which expands during this phase from itscollapsed position 19a to the extended position 19.

In order to assure that an adequate volume of ventilating gas issupplied to the system it is usually customary to supply an amountslightly in excess of the required volume. Under these conditions at theend of each exhalation phase the upper surface 28 of the bellows device13 will be slightly higher than after the previous cycle. Eventually thebellows surface 28 reaches its fully'extended position and at this pointthe tension member 26 tightens and lifts the valve member 22 oif itsseat 23. This opens the anesthesia system to atmosphere and per- '-mitsthe extra gas supplied during the exhalation phase to be bled off to theoutside. As soon as the pressure is applied for the inhalation phase thebellows device again is moved toward collapsing position and the valve22 is closed resulting in application of pressure to the system toprovide the inhalation phase as previously described.

The valve 21 may also function as a safety device to prevent a negativepressure being developed in the anesthesia system. Should for somereason the supply of anesthesia gas into the system be inadequate tosupply the full ventilating volume required, the bellows device 13 wouldcollapse more at each succeeding cycle until eventually a completelycollapsed position such as indicated by the position of the uppersurface 28b would occur. At this position natural inhalation by thepatient would create a slight negative pressure in the anesthesiasystem. If this condition were not noted and corrected an inadequatesupply of ventilating gas would be available in the system to supply thepatient. In this event the valve 22 would open under the negativepressure developed and permit air to enter the anesthesia machine systemand supplement the supply of gas being provided through the connector10.

It will be evident that unassisted or spontaneous breath ing also causesexpansion and contraction of the bellows 13 so that the volume isdirectly indicated under these conditions as well. When flow ofanesthesia gas is greater than required, distention of the expansiblecontainer causes the relief valve to bleed off the excess'gas.

From the foregoing it will be evident that I have provided an improveddevice for lung ventilation of a patient during anesthesia. By means ofthis equipment it is easy to take readings of the volume of ventilationcontinuously throughout the period when anesthesia is beingadministered. The visibility of the apparatus from all positionsprovides increased safety for the patient and assures that adequateventilation will be supplied. More accurate adjustment of supply may beused, since any inadequate fiow is shown by the gradual lowering of theposition of the indicator after inhalation. Correction of the flow maybe made long before the condition becomes urgent. The combined safetyvalve and indicator bellows unit provides automatically for overflow ofexcess anesthesia gas without requiring attention on the part of theanesthetist. Also the construction of the valve device assures anemergency source of air for the patient through the system in the eventthat the anesthesia system should provide an in adequate supply ofventilating gas. All of these advantages permit the anesthetist tomaintain a more constant check on the patient because less time andattention is required to maintain proper operation of the equipment. Atthe same time the feel of the system is retained so that the anesthetistdoes not need to learn new techniques of operation. Furthermore, theprecise proportions of gases used in the anesthesia mixture is preservedbecause air from the squeeze bag is not able to enter the gas system andcommingle with the anesthetic mixture. This also prevents theaccumulation of condensate in the squeeze bag.

I claim:

- 1. In a lung ventilating system having conduit means for conveyinglung ventilating gases to and from a patient,

'a bellows unit arranged to collapse and expand generally vertically andwith its interior in communication with said conduit means and providingfor development of pressure in the conduit means by a verticalcollapsing stroke of the bellows unit for assisting inhalation by thepatient and providing for vertical expansion of the bellows under theinfluence of the patients exhalation, a chamber surrounding the bellowsand pneumatically isolated from the interior of the bellows unit duringsaid collapsing stroke, the chamber having a transparent wall throughwhich collapsing and expanding strokes of the bellows are visible, a bagadapted to be manually squeezed in a hand of the operator and connectedto the interior of said chamber to effect said collapsing stroke of thebellows and to expand under the influence of expansion of the bellows,the bag thereby being free to transmit the feel of the patientsbreathing to the hand of the operator, and breathing volume indicatorscale means for reading the bellows collapsing and expansion strokes asvisible through the transparent chamber wall concurrently with feelingthe patients breathing in the collapsing and expansion of the bag.

2. In a lung ventilating system having conduit means for conveying lungventilating gasesto and from a patient, a bellows unit arranged tocollapse and expand generally vertically and with a surroundingtransparent chamber wall cooperating to provide internal and externalpressure chambers, the conduit means being connected with one of saidchambers to receive gases therefrom during inhalation and to delivergases thereto during exhalation, abag adapted to be manually squeezed ina hand of the operator and connected with the other of said chambers todevelop pressure therein by collapse of the I bag for transmissionthrough the bellows to said one chamber and thus to the conduit meansfor inhalation by the patient and to expand by rise in pressure in saidother chamber under the influence of exhaba-tion of gases by the patientthrough the conduit means into said one chamber, the bag thereby beingfree to transmit the feel of the patients breathing to the hand of theoperator, said chambers being pneumatically isolated from each otherduring operation of the bag to develop pressure in said other chamber,and breathing volume indicator scale means for reading the bellowsmovement during inhalation and during exhalation as visible through thetransparent chamber wall concurrently with feeling the patientsbreathing in the collapsing and expansion of the bag.

3. In a lung ventilating system having conduit means for conveying lungventilating gases to and from a patient, a bellows unit arranged tocollapse and expand generally vertically and with a surroundingtransparent chamber wall cooperating to provide internal and externalpressure chambers, the conduit means being connected with one of saidchambers to receive gases therefrom during inhalation and to delivergases thereto during exhalation, a bag adapted to be manually squeezedin a hand of the operator and connected with the other of said chambersto develop pressure therein by collapse of the bag for transmissionthrough the bellows to said one chamber and thus to the conduit meansfor inhalation by the patient and to expand by rise in pressure in saidother chamber under the influence of exhalation of gases by the patientthrough the conduit means into said one chamber, the bag thereby beingfree to transmit the feel of the patients breathing to the hand of theoperator, said chambers being pneumatically isolated from each otherduring operation of .the bag to develop pressure in said other chamber,overflow valve means for discharging excess exhalation gas from said onechamber, and breathing volume indicator scale means for reading bellowsmove ment during inhalation and during exhalation as visible through thetransparent chamber wall concurrently with feeling the patientsbreathing in the collapsing and expansion of the bag.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS8/1953 Great Britain.

RICHARD A. GAUDET, Primary Examiner.

1. IN A LUNG VENTILATING SYSTEM HAVING CONDUIT MEANS FOR CONVEYING LUNGVENTILATING GASES TO AND FROM A PATIENT, A BELLOWS UNIT ARRANGED TOCOLLAPSE AND EXPAND GENERALLY VERTICALLY AND WITH ITS INTERIOR INCOMMUNICATION WITH SAID CONDUIT MEANS AND PROVIDING FOR DEVELOPMENT OFPRESSURE IN THE CONDUIT MEANS BY A VERTICAL COLLAPSING STROKE OF THEBELLOWS UNIT FOR ASSISTING INHALATION BY THE PATIENT AND PROVIDING FORVERTICAL EXPANSION OF THE BELLOWS UNDER THE INFLUENCE OF THE PATIENT''SEXHALATION, A CHAMBER SURROUNDING THE BELLOWS AND PNEUMATICALLY ISOLATEDFROM THE INTERIOR OF THE BELLOWS UNIT DURING SAID COLLAPSING STROKE, THECHAMBER HAVING A TRANSPARENT WALL THROUGH WHICH COLLAPSING AND EXPANDINGSTROKES OF THE BELLOWS ARE VISIBLE, A BAG ADAPTED TO BE MANUALLYSQUEEZED IN A HAND OF THE OPERATOR AND CONNECTED TO THE INTERIOR OF SAIDCHAMBER TO EFFECT SAID COLLAPSING STROKE OF THE BELLOWS AND TO EXPANDUNDER THE INFLUENCE OF EXPANSION OF THE BELLOWS, THE BAG THEREBY BEINGFREE TO TRANSMIT THE "FEEL" OF THE PATIENT''S BREATHING TO THE HAND OFTHE OPERATOR, AND BREATHING VOLUME INDICATOR SCALE MEANS FOR READING THEBELLOWS COLLAPSING AND EXPANSION STROKES AS VISIBLE THROUGH THETRANSPARENT CHAMBER WALL CONCURRENTLY WITH "FEELING" THE PATIENT''SBREATHING IN THE COLLAPSING AND EXPANSION OF THE BAG.